Built on top of the Viaduc des Arts, the Promenade Plantée is somewhat of a secret garden in Paris. It is a beautiful garden walkway created along the top of the old railway viaduct that runs for about 4.5 km from the Bastille to the Bois de Vincennes. If you want to escape the maddening crowd in Paris, this is a great place to enjoy a quiet stroll. Read more about the Promenade Plantée .